Ni / c catalyst preparation method and application

Abstract

The application relates to a preparation method and application of a Ni / C catalyst, in particular to application of the Ni / C catalyst in hydrogenation of o-cresol into o-methylcyclohexanol, and belongs to the technical field of preparation of catalytic hydrogenation catalysts. The Ni / C catalyst used in the reaction system is obtained through one-step pyrolysis by taking Ni-BTC as a self-sacrificial template. The preparation raw material of the Ni / C catalyst is extensive, the price is low, the whole catalyst preparation process is simple, convenient and controllable, and the Ni / C catalyst is suitable for large-scale preparation. The Ni / C catalyst with high catalytic activity and selectivity is in-situ formed through pyrolysis at a lower temperature, the catalyst stability is very good, no obvious deactivation phenomenon is generated after 7 cycles of reaction, and the catalyst is easy to be separated through magnetic adsorption after the catalytic reaction is completed due to the magnetism of the catalyst, and the catalyst is convenient to recycle.

Description

Technical Field

[0001] This invention belongs to the field of catalytic hydrogenation catalyst preparation technology, and relates to a method for preparing a Ni / C catalyst and its application, particularly the application of a Ni / C catalyst in the hydrogenation of o-cresol to o-methylcyclohexanol. Background Technology

[0002] With the increasing scarcity of fossil fuels and the gradual deterioration of the global environment, the demand for obtaining energy and chemicals from lignocellulosic biomass and developing economical renewable raw materials is growing. Lignin is an important component of lignocellulosic acid and can be converted into hundreds of phenolic compounds through various methods such as pyrolysis, hydrogenation, oxidation, and biocatalysis. Lignin-derived phenolic substances, such as phenols, cresols, and guaiacols, are important components of bio-oils. Due to the strong corrosiveness, instability, and high viscosity of bio-oils, they require further processing and conversion before they can be effectively utilized. Currently, many researchers both domestically and internationally have studied the physicochemical characteristics of bio-oils and their hydrogenation reactions. Phenolic compounds, as compounds abundant in bio-oils and difficult to react, are often used as model compounds in hydrogenation reaction studies. During hydrogenation, phenolic compounds can yield cyclohexanol, cyclohexanone, and their derivatives, while further hydrogenation can yield cyclohexyl compounds. o-Cresol, as one of the simpler phenolic model compounds in lignin, is widely available and has huge reserves, providing more possibilities for its industrial application. One of its hydrogenation products, o-methylcyclohexanol, is an important chemical intermediate. Its main use is in the synthesis of o-methylcyclohexyl acetate, an excellent solvent for hydrogen peroxide synthesis. It is also used as a solvent for rubber and resins, and as a colorant in pharmaceuticals and food. In the reaction of o-cresol hydrogenation to o-methylcyclohexanol, the catalyst plays a crucial role.

[0003] To date, metal catalysts remain one of the commonly used hydrogenation catalysts. Among them, noble metal catalysts mainly include Pd, Pt, and Ru. However, traditional Pd / C noble metal catalysts used in the hydrogenation of o-cresol to o-methylcyclohexanol suffer from low selectivity and easy deactivation under reaction conditions. Typically, when these noble metals are used as active components to catalyze the formation of alcohols from phenolic compounds, they require modification, leading to cumbersome catalyst preparation steps. Furthermore, noble metals are expensive, scarce, and costly to produce, and their recovery during use is difficult, resulting in low utilization rates. Therefore, noble metals are not suitable for large-scale industrial production. In contrast, non-noble metal catalysts, represented by Fe, Co, and Ni, have advantages such as abundant reserves, low cost, and environmental friendliness, and exhibit excellent catalytic activity and selectivity in hydrogenation reactions, making them promising alternatives to noble metal catalysts. Patent CN115155645B discloses a Co / HCN catalyst for the catalytic hydrogenation of o-cresol to o-methylcyclohexanol. Under conditions of a reaction temperature of 210-225℃, a reaction pressure of 3.0-4.0 MPa, and a reaction time of 2 h, the o-cresol conversion rate reaches over 90%, and the o-methylcyclohexanol selectivity reaches over 99%. Although excellent catalytic activity is achieved, the reaction temperature is too high, resulting in significant energy consumption. Patent CN107537497A discloses a catalyst prepared by adding cobalt powder to nickel-aluminum alloy powder for the hydrogenation of o-cresol to o-methylcyclohexanol. Under reaction conditions of 80-180℃, a reaction time of 5-10 h, and a hydrogen pressure of 2-6 MPa, the o-cresol selectivity reaches over 90%, and the o-methylcyclohexanol selectivity reaches over 96%. Although the reaction conditions are relatively mild, the catalyst activity is not high enough, requiring a longer reaction time.

[0004] In summary, the current hydrogenation reaction of o-cresol to o-methylcyclohexanol still faces challenges such as high cost, easy catalyst deactivation, and demanding reaction conditions. Therefore, the research and development of an economical and efficient non-precious metal catalyst is of paramount importance. Summary of the Invention

[0005] This invention addresses the problems of high cost, easy catalyst deactivation, and harsh reaction conditions in the hydrogenation of o-cresol to o-methylcyclohexanol, and proposes a novel Ni / C catalyst preparation method and its application.

[0006] To achieve the above objectives, the present invention is implemented using the following technical solution:

[0007] A method for preparing a Ni / C catalyst includes the following steps:

[0008] Step 1: Add 1,3,5-benzenetricarboxylic acid to a ternary mixed solvent of deionized water, N,N-dimethylformamide, and ethylene glycol. After it dissolves, add nickel nitrate hexahydrate and dissolve to obtain a clear mixed solution.

[0009] Step 2: Transfer the above mixed solution to a hydrothermal reactor with a polytetrafluoroethylene liner for hydrothermal reaction. After the hydrothermal reaction is completed, allow it to cool naturally to room temperature, centrifuge to separate the product, wash it several times with methanol, and dry it to obtain the Ni-BTC precursor.

[0010] Step 3: The above Ni-BTC precursor is calcined under argon to obtain the Ni / C catalyst.

[0011] Preferably, the concentration of 1,3,5-benzenetricarboxylic acid in the mixed solution of step one is 0.02-0.03 mol / L, and the concentration of nickel nitrate hexahydrate is 0.03-0.07 mol / L.

[0012] Preferably, the volume ratio of deionized water:N,N-dimethylformamide:ethylene glycol in the mixed solvent of step one is (2-11):(4-22):3.

[0013] Preferably, in step two, the hydrothermal reaction temperature is 140-160℃, the hydrothermal reaction time is 9-11h, the centrifugation speed is 7000-9000r / min, the centrifugation time is 2-8min, the washing frequency is 3-5 times, the drying temperature is 60-80℃, and the drying time is 8-16h.

[0014] Preferably, in step three, the calcination temperature is 415-455℃, the calcination time is 2.5-3.5h, and the calcination atmosphere is argon.

[0015] This invention proposes the application of the Ni / C catalyst prepared by the method in the hydrogenation of o-cresol to o-methylcyclohexanol. The reaction conditions are as follows: hydrogenation reaction temperature is 160-170℃, reaction pressure is 1.5-2.5MPa, rotation speed is 200-300r / min, solvent is cyclohexane, o-cresol concentration is 0.9-1.1wt.%, and Ni / C catalyst addition is 3-7g / L of reaction solution.

[0016] The Ni-based catalyst proposed in this invention exhibits excellent activity, selectivity, and stability in the hydrogenation of o-cresol to o-methylcyclohexanol. Using Ni-BTC as a self-sacrificing template, the morphology of the Ni-BTC precursor is maintained after a one-step pyrolysis. The Ni-BTC precursor is synthesized in a mixed solvent of polar and nonpolar protons. By adjusting the ratio of deionized water, N,N-dimethylformamide, and ethylene glycol in the ternary mixed solvent, the degree of deprotonation of 1,3,5-benzenetricarboxylic acid in the solvent is altered, thereby changing the coordination between nickel ions and 1,3,5-benzenetricarboxylic acid, further modifying the morphology and size of the Ni-BTC precursor, and thus controlling the microstructure and surface properties of the Ni / C catalyst obtained after calcination. The Ni-BTC precursor prepared by this invention has a hollow structure, conforming to the Ostwald ripening mechanism. Under high-temperature hydrothermal conditions, nickel ions first coordinate with 1,3,5-benzenetricarboxylic acid to form amorphous solid spheres. These amorphous solid spheres gradually crystallize under hydrothermal conditions, forming a more thermodynamically stable phase. During crystallization, the internal material of the spheres gradually dissolves and diffuses to the surface, eventually forming a hollow structure. This hollow structure not only provides abundant and readily available metallic structural sites but also facilitates the transport and transfer of substrate and product molecules, thereby improving the catalytic hydrogenation performance of the catalyst. In the subsequent pyrolysis process, after reaching the decomposition temperature of the Ni-BTC precursor, the organic ligand 1,3,5-phenyltricarboxylic acid decomposes into water and carbon dioxide. The excess carbon atoms generate an amorphous carbon matrix that holds the Ni... 2+ Encapsulation. And at a suitable pyrolysis temperature, the carbon matrix will encapsulate Ni. 2+ In-situ reduction to elemental Ni is achieved, with a large number of Ni nanoparticles well dispersed in the carbon matrix without significant aggregation. Simultaneously, the transition metal catalyzes the formation of graphitic carbon from amorphous carbon.

[0017] Compared with the prior art, the advantages and positive effects of the present invention are as follows:

[0018] 1. The Ni / C catalyst proposed in this invention has widely available and inexpensive raw materials, and the entire catalyst preparation process is simple, convenient, and controllable, making it suitable for large-scale preparation.

[0019] 2. The appropriate ratio of deionized water, N,N-dimethylformamide, and ethylene glycol can realize the transformation of Ni-BTC precursor from solid spheres to hollow spheres, and the hollow structure of Ni-BTC precursor can be maintained after calcination. This not only provides abundant and easily accessible metal structural sites, but also facilitates the transport and transfer of substrate and product molecules, thereby improving the activity of the catalyst.

[0020] 3. The Ni active component in the obtained catalyst is embedded in the carbon matrix without obvious aggregation, and the Ni nanoparticles are well dispersed.

[0021] 4. The catalyst has excellent stability. After seven cycles, there was no obvious deactivation. The conversion rate and selectivity remained basically unchanged. Moreover, because the catalyst itself is magnetic, it can be easily separated by magnetic adsorption after the catalytic reaction is completed, making recovery convenient. Attached Figure Description

[0022] Figure 1 This is a SEM image of the Ni-BTC precursor in Example 1.

[0023] Figure 2 This is a SEM image of the Ni / C catalyst in Example 1.

[0024] Figure 3 The image shows the XRD pattern of the Ni / C catalyst in Example 1.

[0025] Figure 4 This is a SEM image of the Ni-BTC precursor in Example 3.

[0026] Figure 5 This is a SEM image of the Ni / C catalyst in Example 3.

[0027] Figure 6 The image shows the XRD pattern of the Ni / C catalyst in Example 3.

[0028] Figure 7 The graph shows the cycle stability test results of the Ni / C catalyst in Example 4.

[0029] Figure 8 The image shows the SEM image of the Ni-BTC precursor in Comparative Example 1.

[0030] Figure 9 The image shows the SEM image of the Ni-BTC precursor in Comparative Example 2.

[0031] Figure 10 The image shows the SEM image of the Ni / C catalyst in Comparative Example 2. Detailed Implementation

[0032] To better understand the above-mentioned objectives, features, and advantages of the present invention, the present invention will be further described below with reference to specific embodiments. It should be noted that, unless otherwise specified, the embodiments and features described in these embodiments can be combined with each other.

[0033] Numerous specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways than those described herein, and therefore the invention is not limited to the specific embodiments disclosed in the following specification.

[0034] Example 1

[0035] This embodiment provides a specific preparation process of the Ni / C catalyst and its application in the liquid-phase hydrogenation of o-cresol. The catalyst preparation process is as follows.

[0036] (1) Synthesis of Ni-BTC precursor: First, a mixed solvent of deionized water, N,N-dimethylformamide, and ethylene glycol in a volume ratio of 5:10:3 was prepared, and 1,3,5-benzenetricarboxylic acid was added. After the 1,3,5-benzenetricarboxylic acid was completely dissolved, nickel nitrate hexahydrate was added, and a clear mixed solution was obtained after dissolution. The concentration of 1,3,5-benzenetricarboxylic acid in the mixed solution was 0.025 mol / L, and the concentration of nickel nitrate hexahydrate was 0.05 mol / L. Then, the mixed solution was transferred to a hydrothermal reactor with a polytetrafluoroethylene liner and placed in a forced-air drying oven. The hydrothermal reaction was carried out at 150℃ for 10 h. After the hydrothermal reaction was completed, it was naturally cooled to room temperature. The green precipitate was separated by centrifugation at a speed of 8000 r / min for 5 min. After washing with methanol 4 times, it was dried in an oven at 70℃ for 12 h.

[0037] (2) Preparation of Ni / C catalyst: Weigh 0.65g of Ni-BTC powder into a boat, place it in a high-temperature tube furnace, seal it, remove the air from the tube, replace it with argon three times, adjust the gas flow to 60mL / min, program the temperature to 435℃ and calcine for 3h at a heating rate of 5℃ / min, and allow it to cool naturally after calcine to finally obtain the Ni / C catalyst.

[0038] The above-mentioned Ni / C catalyst was used in the liquid-phase hydrogenation of o-cresol to prepare o-methylcyclohexanol. Under the conditions of hydrogen pressure of 2 MPa, reaction temperature of 165 °C, stirring speed of 250 r / min, o-cresol concentration of 1 wt.%, and Ni / C catalyst addition of 5 g / L reaction solution, the reaction was carried out for 40 min. The o-cresol conversion rate was 99.5%, and the o-methylcyclohexanol selectivity was 99.9%.

[0039] The reaction conditions and catalytic effects of the catalyst prepared in this embodiment were compared with those of existing catalysts, and the results are shown in Table 1.

[0040] Table 1. Comparison of the performance of different catalysts in the hydrogenation of o-cresol to o-methylcyclohexanol

[0041]

[0042] As shown in Table 1, the catalyst prepared in this embodiment achieves higher reaction conversion and product selectivity under mild reaction conditions and with a shorter reaction time, indicating that the catalyst prepared in this embodiment possesses high catalytic activity. In principle, the hollow structure of the catalyst prepared in this embodiment not only provides abundant and easily accessible metal structural sites but also facilitates the transport and transfer of substrate and product molecules. Furthermore, because the Ni active component in the obtained catalyst is embedded in the carbon matrix without significant aggregation, the Ni nanoparticles are well dispersed, exposing more catalytic active sites in the catalyst. Therefore, the catalyst prepared in this embodiment exhibits excellent performance and has good industrial application potential in the hydrogenation of o-cresol to o-methylcyclohexanol.

[0043] Figure 1 The image shows the SEM image of the Ni-BTC precursor in Example 1. The precursor has a spherical microstructure with a rough surface. Some spheres even have a relatively obvious porous structure with a size of about 2-6 μm. Partially broken shell structures can also be observed.

[0044] Figure 2 The image shows the SEM image of the Ni / C catalyst in Example 1. It can be seen from the image that the morphology of the precursor can be basically maintained after calcination, with a size of about 1.5-5.5 μm, and the presence of hollow structure can be observed from the broken spheres.

[0045] Figure 3 The XRD pattern of the Ni / C catalyst in Example 1 shows three peaks at 2θ of 44.5°, 51.8°, and 76.4°, which belong to the diffraction peaks of Ni(111), Ni(200), and Ni(220), respectively, confirming that Ni... 2+ It has been successfully converted into Ni nanoparticles. In addition, a weak, broad peak belonging to graphitic carbon was also found at 25.9°.

[0046] Example 2

[0047] This embodiment provides the preparation process of Ni / C catalyst and its application in the liquid-phase hydrogenation of o-cresol to prepare o-methylcyclohexanol. Unless otherwise specified, this embodiment is consistent with Example 1.

[0048] (1) Synthesis of Ni-BTC precursor: First, a mixed solvent of deionized water, N,N-dimethylformamide, and ethylene glycol in a volume ratio of 11:22:3 was prepared, and 1,3,5-benzenetricarboxylic acid was added. After the 1,3,5-benzenetricarboxylic acid was completely dissolved, nickel nitrate hexahydrate was added, and a clear mixed solution was obtained after dissolution. The concentration of 1,3,5-benzenetricarboxylic acid in the mixed solution was 0.03 mol / L, and the concentration of nickel nitrate hexahydrate was 0.07 mol / L. Then, the mixed solution was transferred to a hydrothermal reactor with a polytetrafluoroethylene liner and placed in a forced-air drying oven. The hydrothermal reaction was carried out at 160℃ for 9 h. After the hydrothermal reaction was completed, it was naturally cooled to room temperature. The green precipitate was separated by centrifugation at a speed of 9000 r / min for 2 min. After washing with methanol 5 times, it was dried in an oven at 80℃ for 8 h.

[0049] (2) Preparation of Ni / C catalyst: 0.65g of Ni-BTC powder was weighed into a boat, placed in a high-temperature tube furnace, sealed, and the air inside the tube was extracted. After purging with argon three times, the gas flow rate was adjusted to 60mL / min, and the temperature was programmed to 455℃ for 2.5h at a heating rate of 5℃ / min. After calcination, the temperature was allowed to drop naturally to obtain the Ni / C catalyst.

[0050] The above-mentioned Ni / C catalyst was applied to the reaction of liquid-phase hydrogenation of o-cresol to prepare o-methylcyclohexanol. Under the conditions of hydrogen pressure of 1.5 MPa, reaction temperature of 170 °C, stirring speed of 200 r / min, reaction time of 35 min, o-cresol concentration of 0.9 wt.%, and Ni / C catalyst addition of 7 g / L reaction solution, the o-cresol conversion rate was 96.3% and the o-methylcyclohexanol selectivity was 99.4%.

[0051] Example 3

[0052] This embodiment provides the preparation process of Ni / C catalyst and its application in the liquid-phase hydrogenation of o-cresol to prepare o-methylcyclohexanol. Unless otherwise specified, this embodiment is consistent with Example 1.

[0053] (1) Synthesis of Ni-BTC precursor: First, a mixed solvent of deionized water, N,N-dimethylformamide, and ethylene glycol in a volume ratio of 2:4:3 was prepared, and 1,3,5-benzenetricarboxylic acid was added. After the 1,3,5-benzenetricarboxylic acid was completely dissolved, nickel nitrate hexahydrate was added. After dissolution, a clear mixed solution was obtained, in which the concentration of 1,3,5-benzenetricarboxylic acid was 0.02 mol / L and the concentration of nickel nitrate hexahydrate was 0.03 mol / L. Then, the mixed solution was transferred to a hydrothermal reactor with a polytetrafluoroethylene liner and placed in a forced-air drying oven. The hydrothermal reaction was carried out at 140℃ for 11 h. After the hydrothermal reaction was completed, it was naturally cooled to room temperature. The green precipitate was separated by centrifugation at a speed of 7000 r / min for 8 min. After washing three times with methanol, it was dried in an oven at 60℃ for 16 h.

[0054] (2) Preparation of Ni / C catalyst: 0.65g of Ni-BTC powder was weighed into a boat, placed in a high-temperature tube furnace, sealed, and the air inside the tube was extracted. After purging with argon three times, the gas flow rate was adjusted to 60mL / min, and the temperature was programmed to 415℃ for calcination for 3.5h at a heating rate of 5℃ / min. After calcination, the temperature was allowed to drop naturally to obtain the Ni / C catalyst.

[0055] The above-mentioned Ni / C catalyst was used in the experiment of preparing o-methylcyclohexanol by liquid-phase hydrogenation of o-cresol. Under the conditions of hydrogen pressure of 2.5 MPa, reaction temperature of 160℃, rotation speed of 300 r / m, reaction time of 45 min, o-cresol concentration of 1.1 wt.%, and Ni / C catalyst addition of 3 g / L reaction solution, the o-cresol conversion rate was 93.8% and the o-methylcyclohexanol selectivity was 99.1%.

[0056] Figure 4 The image shows a SEM image of the Ni-BTC precursor in Example 3. The image shows a spherical morphology with a smooth surface. The core-shell and hollow structure can be observed from the broken spheres, with a size of approximately 3-8 μm.

[0057] Figure 5 The image shows a SEM image of the Ni / C catalyst in Example 3. It can be seen from the image that the morphology of the precursor can be basically maintained after calcination, with a size of approximately 1-5 μm.

[0058] Figure 6 The XRD pattern of the Ni / C catalyst in Example 3 is basically the same as that in Example 1, but the broad peak at 25.9° belonging to graphite carbon is not as obvious as in Example 1.

[0059] Example 4

[0060] In this embodiment, the catalyst from Example 1 is used multiple times for recycling to verify its stability. After the reaction is complete, the catalyst is separated from the liquid by utilizing its inherent magnetism. A magnet is placed close to the outside of the quartz glass liner, and the supernatant is slowly poured off, leaving only the catalyst inside the reaction liner. Fresh reaction solution is then added, the magnet is removed, and the catalyst is mixed and soaked in the reaction solution before the reaction continues under the same conditions.

[0061] Figure 7 In this embodiment, the catalyst recovery reaction results were obtained under the following conditions: reaction pressure 2 MPa, reaction temperature 165 °C, rotation speed 250 r / min, reaction time 40 min, o-cresol concentration 1 wt.%, and Ni / C catalyst addition 5 g / L. Figure 7 It can be seen that the catalytic performance remains stable after 7 cycles.

[0062] Comparative Example 1

[0063] This comparative example uses a binary mixed solvent of ethylene glycol and N,N-dimethylformamide to synthesize a Ni-BTC precursor, which is then calcined to obtain a Ni / C catalyst. This catalyst is used in the liquid-phase hydrogenation of o-cresol to prepare o-methylcyclohexanol to verify the effect of solvent type on catalyst performance within the scope of protection of this invention.

[0064] (1) Synthesis of Ni-BTC precursor: First, a mixed solvent of N,N-dimethylformamide and ethylene glycol in a volume ratio of 1:2 was prepared, and 1,3,5-benzenetricarboxylic acid was added. After the 1,3,5-benzenetricarboxylic acid was completely dissolved, nickel nitrate hexahydrate was added. After dissolution, a clear mixed solution was obtained, in which the concentration of 1,3,5-benzenetricarboxylic acid was 0.025 mol / L and the concentration of nickel nitrate hexahydrate was 0.05 mol / L. Then, the mixed solution was transferred to a hydrothermal reactor with a polytetrafluoroethylene liner, placed in a forced-air drying oven, and reacted at 150℃ for 10 h. After the hydrothermal reaction was completed, it was naturally cooled to room temperature. The green precipitate was separated by centrifugation at a speed of 8000 r / min for 5 min. After washing with methanol 4 times, it was dried in an oven at 70℃ for 12 h.

[0065] (2) Preparation of Ni / C catalyst: 0.65g of Ni-BTC powder was weighed into a boat, placed in a high-temperature tube furnace, sealed, and the air inside the tube was extracted. After purging with argon three times, the gas flow rate was adjusted to 60mL / min, and the temperature was programmed to 435℃ for calcination for 3h at a heating rate of 5℃ / min. After calcination, the temperature was allowed to drop naturally to obtain the Ni / C catalyst.

[0066] The above-mentioned Ni / C catalyst was used in the experiment of preparing o-methylcyclohexanol by liquid-phase hydrogenation of o-cresol. The reaction conditions were the same as in Example 1. The conversion rate of o-cresol was 22.8%, and the selectivity of o-methylcyclohexanol was 88.4%.

[0067] Figure 8 The image shows a SEM image of the Ni-BTC precursor in Comparative Example 1. The image shows that the morphology consists mostly of irregularly aggregated spherical small particles, as well as a few large particles.

[0068] Comparative Example 2

[0069] This comparative example adjusts the ratio of the ternary mixed solvent, uses the obtained product as a comparison, and focuses on the performance of the final catalyst to verify the influence of the solvent ratio on the catalyst performance within the scope of protection of this invention.

[0070] (1) Synthesis of Ni-BTC precursor: First, a mixed solvent of deionized water, N,N-dimethylformamide, and ethylene glycol in a volume ratio of 1:2:3 was prepared, and 1,3,5-benzenetricarboxylic acid was added. After the 1,3,5-benzenetricarboxylic acid was completely dissolved, nickel nitrate hexahydrate was added. After dissolution, a clear mixed solution was obtained, in which the concentration of 1,3,5-benzenetricarboxylic acid was 0.025 mol / L and the concentration of nickel nitrate hexahydrate was 0.05 mol / L. Then, the mixed solution was transferred to a hydrothermal reactor with a polytetrafluoroethylene liner and placed in a forced-air drying oven. The reaction was carried out at 150℃ for 10 h. After the hydrothermal reaction was completed, it was naturally cooled to room temperature. The green precipitate was separated by centrifugation at a speed of 8000 r / min for 5 min. After washing with methanol 4 times, it was dried in an oven at 70℃ for 12 h.

[0071] (2) Preparation of Ni / C catalyst: 0.65g of Ni-BTC powder was weighed into a boat, placed in a high-temperature tube furnace, sealed, and the air inside the tube was extracted. After purging with argon three times, the gas flow rate was adjusted to 60mL / min, and the temperature was programmed to 435℃ for calcination for 3h at a heating rate of 5℃ / min. After calcination, the temperature was allowed to drop naturally to obtain the Ni / C catalyst.

[0072] The above-mentioned Ni / C catalyst was used in the experiment of preparing o-methylcyclohexanol by liquid-phase hydrogenation of o-cresol. The reaction conditions were the same as in Example 1. The conversion rate of o-cresol was 46.6%, and the selectivity of o-methylcyclohexanol was 96.3%.

[0073] Figure 9 The image shows a SEM image of the Ni-BTC precursor in Comparative Example 2. The image shows a spherical morphology with a size of approximately 2-4 μm, and some of the broken spheres appear to be hollow structures.

[0074] Figure 10The image shows the SEM image of the Ni / C catalyst in Comparative Example 2. It can be seen from the image that the morphology can be basically maintained after calcination, with a size of about 1-3.5 μm, and the partially broken spheres show a hollow structure.

[0075] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any other way. Any person skilled in the art may make changes or modifications to the above-disclosed technical content to create equivalent embodiments for application in other fields. However, any simple modifications, equivalent changes, and modifications made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the protection scope of the present invention.

Claims

1. Use of a Ni / C catalyst for the hydrogenation of o-cresol to o-methylcyclohexanol, characterized in that, The preparation steps of the Ni / C catalyst are as follows: Step one: 1,3,5-benzene tricarboxylic acid is added into a ternary mixed solvent of deionized water, N,N-dimethylformamide and ethylene glycol, and then nickel nitrate hexahydrate is added after the dissolution of 1,3,5-benzene tricarboxylic acid, and a clear mixed solution is obtained after dissolution; Step two: the mixed solution obtained in step one is subjected to hydrothermal reaction, and after the hydrothermal reaction is completed, it is naturally cooled to room temperature, centrifuged, and the obtained green product is washed with methanol for several times and dried to obtain a Ni-BTC precursor; Step three: the Ni-BTC precursor is calcined under argon to obtain a Ni / C catalyst; In step one, the concentration of 1,3,5-benzene tricarboxylic acid in the mixed solution is 0.02-0.03 mol / L, and the concentration of nickel nitrate hexahydrate is 0.03-0.07 mol / L; the volume ratio of deionized water, N,N-dimethylformamide and ethylene glycol in the mixed solvent is (2-11):(4-22):

3.

2. Use according to claim 1, characterized in that, In step two, the hydrothermal reaction temperature is 140-160℃, the hydrothermal reaction time is 9-11h, the centrifugal speed is 7000-9000r / min, the centrifugal time is 2-8min, the washing times is 3-5 times, the drying temperature is 60-80℃, and the drying time is 8-16h.

3. Use according to claim 1, characterized in that, In step three, the calcination temperature is 415-455℃, the calcination time is 2.5-3.5h, and the calcination atmosphere is argon.

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